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Voice Quality Testing (VQT) Software


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Test Engineers can now efficiently test voice quality with a common platform and common software, thereby avoiding purchasing dedicated software and equipment for various technologies. The test tools provide the means of sending and receiving speech signals through various network interfaces.

GL's Voice Quality Testing (VQT) software supports the next-generation voice quality testing standard for fixed, mobile and IP-based networks using POLQA (ITU-T P.863), PESQ (ITU-T P.862), PESQ LQ / LQO (P.862.1), PESQ WB (P.862.2), PAMS (ITU-T P.800), and PSQM/PSQM+ (ITU-T P.861).

PESQ provides an objective measurement of subjective listening tests on telephony systems. PAMS predicts overall subjective listening quality (a human's perception of quality) without requiring actual subjective testing (a very expensive and time-consuming process). PSQM predicts subjective quality of speech codecs without requiring subjective testing.

POLQA, Perceptual Objective Listening Quality Analysis, is the successor of PESQ (ITU-T P.862) analysis and the next generation voice quality testing standard for fixed, mobile and IP-based networks. POLQA, based on ITU standard, ITU-T P.863, supports the latest HD-quality speech coding and network transport technology, with higher accuracy for 3G, 4G/LTE and VoIP networks. The VQT supports analysis using POLQA algorithm for NB (8000 sampling), WB (16000 sampling), and SWB (Super Wideband) (48000 sampling) in both manual and automated testing.

For additional information on ITU Algorithms supported by GL's VQT, refer to ITU Algorithms webpage.

The VQT application is available with the following options:

  • PESQ
  • PESQ with POLQA
  • POLQA only

The results of the VQT algorithms, POLQA, PESQ LQ/LQO/WB, PAMS and PSQM, are displayed both in tabular format as well as graphically. Additional analytical results are displayed as part of the assessment such as POLQA MOS, E-Model, Signal Level, SNR, jitter, clipping, noise level, and delay (end to end as well as per speech utterance). All results are saved to file and database for post processing viewing along with sophisticated searching on the results within the VQT application and using the WebViewer™ (remote and local access).

VQT POLQA Measurements and Analysis


The VQT software can work either independently, in conjunction with VQuad™ - Dual UTA HD, or in conjunction with VQuad™ Probe. The VQuad™ Probe HD(combines with VQuad™-Dual UTA - PC into one single box) provides multiple interfaces for connecting to any communication device on a network using an efficient, portable, single box solution.  The VQuad™ Probe HD can work with variety of networks, including Wireless (Bluetooth®, Wi-fi, 3G, 4G, LTE, PTT), VoIP, Analog, and TDM, practically allowing any end-point interfaces to be tested for voice, data, and video quality. Various associated applications (Voice Quality, Video Quality, Data tests, Echo and Delay tests, Fax tests, VBA) works with VQuad™ Probe HD to provide "end-to-end assessment" with additional test and measuring capabilities. All the applications work in conjunction with the VQuad™ for automatically and remotely analysing the captured data and sending the test results to the central database. You can query results remotely or control the tests using web-based WebViewer™.

Main Features

  • Evaluate audio quality with MOS, E-Model, SNR, jitter, clipping, signal level, noise level, and delay measurements
  • Manual or Automated mode of operations using GL's VQuad™, MAPS™, or T1/E1 Analysis Cards
  • Measuring the effect of Packet Jitter in VoIP Network.
  • Analyze the effects of Codec Compression in Wireless Networks
  • Supports PESQ ITU-P.862.2 and POLQA for Wideband
  • POLQA ITU-T P.863 for next generation voice quality testing supporting NB (8000 sampling), WB (16000 sampling) and SWB (Super Wideband) (48000 sampling)
  • Provides PAMS and PSQM (+) Mean Opinion Score (MOS) results.
  • Tabular as well as Graphical Results.
  • Complete automatic logging of all results (both file and database) with the ability to import log back into VQT.
  • All results along with call control information are sent to central database. Query results remotely using the WebViewer™.
  • Support for Central DB Primary and Secondary IP addresses for backup and redundancy
  • Real-time mapping (most countries supported) of results when optional GPS is used in conjunction with VQuad™.
  • Sophisticated search features on the results within the VQT application
  • Command Line Interface (CLI) support to control VQT nodes remotely. Supported on Windows® and Linux

Additional Information

Other Test Solutions with VQuad™


Auto Measurement

The GL VQT may also be executed in Auto Mode. This allows the GL VQT to reside anywhere in a network and monitor multiple user-specified network drives/directories for voice files. GL VQT automatically performs the voice quality algorithms on these recorded voice files and displays the results. Multiple GL VQT Auto-Measurement sessions may be configured, each session with a unique set of requirements and a unique reference voice file. In addition, the user may specify voice files to be saved based on the rating criteria (i.e. if VQT is fair or poor, save the degraded voice file).





Manual Measurement

For manual mode measurement, users can configure a single degraded and reference voice files. VQT automatically performs the voice quality algorithms for the voice files and the current measurement parameters are displayed. Manual mode is limited to single voice file analysis at a time, which are configured from the specified network drives/directories.




Detailed Analysis in GL’s VQT software

The GL VQT software automatically analyzes the degraded voice files while sending the results to the central database. The results associated with the POLQA analysis include POLQA MOS, E-Model, Signal Level, Noise Level, and Jitter.

VQT detailed analysis includes following measurements:

  • Jitter
  • Clipping
  • Level
  • PESQ/Utterance
  • Delay/Utterance


Jitter data is obtained from the time alignment process. The utterance-by-utterance offset must be determined accurately to get a speech quality measure. Jitter is the variation in time offset between reference and degraded utterances. The GL VQT reports utterance offset by providing a minimum/maximum and standard deviation value. These three are measures of jitter in the speech as delivered to the listener. GL also reports the average offset.


Performance Examiner provides a number of diagnostic outputs that relate to the use of muting algorithms and discontinuous transmission. These outputs are generated by comparing the degraded signal to the reference signal.

Muting of a signal typically occurs when an error concealment algorithm at a receiver has insufficient information to replace missing or corrupted data. The muting estimate is provided in terms of the proportion of signal frames that have been muted by the system under test.

Discontinuous transmission (DTX) schemes aim to increase transmission efficiency by ceasing transmission during periods of talker inactivity. Temporal clipping occurs when the voice activity detection (VAD) algorithm in a DTX system misclassifies part of a speech utterance as noise, and replaces it with comfort noise at the receiver.

Front-end clipping refers to the case where the start of an utterance has been clipped. Back-end clipping refers the case where the end of an utterance has been clipped.

Hangover is a term applied to the period after the end of an utterance when a discontinuous transmission scheme continues to transmit as normal, rather than generating comfort noise.


For each measurement levels are calculated for the reference and degraded files. These levels are described below:

Measurement Definition
Active Speech Level (ASL) (dBov) Power Level (RMS) during periods of speech
Mean Noise Level (MNL) (dBov) Power Level (RMS) during periods of silence
RMS Mean Level (dBov) Power Level (RMS) of entire sample
DC Offset (PCM Units) DC Offset of input sample


The following results are interpreted from the data above:

Measurement Definition
Speech Level Gain (dB) Speech Level Gain of the system under test. Calculated: (ASL of degraded signal) minus (ASL of reference signal).
Noise Level Gain (dB) Gain calculated for noise in silent periods. Calculated as (MNL of degraded signal) minus (MNL of reference signal). May differ from the system gain if noise is added or suppressed.



A PESQ/PESQ LQ/PESQ LQO score is available on a per utterance basis. Each sample is broken into distinctive utterances; which GL provides an ITU score for each of the utterances.

For example, front end clipping, which would only affect the 1st utterance, could cause the overall scores to be lower than expected. PESQ/Utterance will indicate this cause.



The delay per utterance results are acquired by comparing the beginning of each utterance in the reference file to the beginning of each utterance in the degraded file. This comparison takes place for each utterance in the reference and degraded files.


Rating Criteria

The user may configure a Rating Criteria for all VQT algorithms as well as the additional analytical results. The rating criteria may be configured for Excellent, Good, Fair, and Poor and the results of the rating criteria may be saved to file for post processing viewing. Thus, the user may view only Fair and Poor results if desired. Full statistics are also available that include all measurement results as well as Rating Criteria results.



VQT system also provides algorithm, rating, and graphical statistics. The tabular statistics includes Min, Max and Average measurements for the complete VQT system results including POLQA, PESQ, PAMS, and PSQM and analysis results (Jitter, Clipping, Speech/Noise level, and more).


The statistics for the VQT system also includes the following graphical statistics:

  • Global Rating History (24 hour) - displays the number of Excellent/Good/Fair/Poor results calculated in past 24 hours.
  • Global Score History (24 hour) - shows the PESQ/PAMS/PSQM scores that are calculated in past 24 hours.
  • Score History Per Auto Instance - shows the PESQ/PAMS/PSQM scores that are calculated in past one hour for the selected auto measurement instance
  • Rating Statistics per Instance - shows graph statistics for each instance.

Command Line Interface (CLI) for remote access

The VQT Command Line Interface (CLI) is designed to remotely access various application functionalities and thus controlling VQT nodes located at various destinations. The supporting commands helps the VQT users to run the application installed on remote PC, get the connection status, run the analysis, load Auto Measurement configuration, start/stop Auto Measurement, save events captured to file, transfer the events captured to client, get any file from server or even get latest log, and other operations. The VQT CLI is supported on Windows® and Linux systems.






Buyer's Guide

Item No. VQuad™ Network Options
VQT002 Voice Quality Testing (PESQ only)
VQT006 VQT w/ POLQA Server License
VQT010 VQuad™ Software (Stand Alone)
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